This invention relates to a large width heat-weldable roof membrane. More particularly, this invention relates to a large width single-ply heat weldable roof membrane comprising at least two thermoplastic olefin (TPO) membranes joined by an intervening fold strip comprising a thermoplastic elastomer material (TPE).
A membrane roofing system generally includes a roof deck which is considered the structural supporting surface of a building extending between the surrounding exterior walls of the building. The roof deck may be constructed from plywood, metal decking or concrete or any other suitable material. Depending upon the construction, the roof deck may extend over the surrounding exterior walls or the roof deck may stop short of the exterior walls thereby forming a parapet wall, i.e., a low retaining wall at the edge of the roof deck. If desired, the membrane roofing system may also include an insulation barrier formed from polyisocyanarate or any other suitable material applied over the roof deck.
To make the roof deck and building weather resistant a single-ply membrane roof may be installed over the roof deck. The single-ply membrane roof refers to a water impermeable single sheet of polymeric material such as thermoplastic olefins, chlorinated polyethylene, polyvinyl chloride, chlorosulfanated polyethylene or ethylene propylene diene rubber (EPDM) having a preapplied hot melt adhesive. The membrane roof has heretofore been installed on the roof deck using a variety of different methods well known in the art.
Because of outstanding weathering resistance and flexibility, cured EPDM based roofing membrane has rapidly gained acceptance.
Typically, the roofing material comes in rolls and is rolled on in strips running the length of the building with a slight overlap between adjacent strips to provide a lap joint. Unfortunately, in the past such roofing material has typically been available only in rolls of relatively narrow width, for example, four feet wide. For a roof of large dimensions, such as 200 feet by 400 feet, the time required to apply the roofing material strips of narrow width becomes excessive and, in light of today""s high labor casts, relatively expensive. To reduce the application time, and hence the cost, of roofing, it is desirable to provide as large a width of single-ply roof membrane, such as forty feet or more wide, as possible. The time required to roof a building in this manner is a mere fraction, of that previously necessary with sheet stock of narrower width, e.g., 4 feet wide. However, one problem with most of the thermoplastic materials that can be used for single ply roofing is that they don""t return to their original shape when they are folded for shipment. For example, there are problems associated with the creases that are formed when the large width single-ply roof membrane is folded. First, the creases present an application problem for the installers. Second, the creased area provides an area that is stressed and can age faster than the non-folded area of the material.
This invention relates to a method and apparatus for providing indefinite length stock of very large width heat weldable membrane, e.g., TPO membrane, from indefinite length stock of relatively narrower width that may be folded for shipment.
Accordingly, it is an object of this invention to provide a large width heat-weldable roof membrane of indefinite length and a method of manufacture. It is another object of this invention to provide a large width single-ply heat weldable roof membrane of indefinite length comprising at least two thermoplastic olefin membranes joined by an intervening fold strip of thermoplastic elastomer material and a method of manufacturing the same.
Briefly, the present invention relates to a large width single-ply heat-weldable roof membrane. The roof membrane includes at least two sheets of a thermoplastic polyolefin and one fold strip of a thermoplastic elastomer. The sheets have side edges. The fold strip is bonded to the sheets to join the sheets and form the large width single-ply roof membrane. The thermoplastic elastomer consists of a highly cross-linked rubbery polymer and a thermoplastic polymer.
The rubbery polymer is comprised of ethylene-propylene-diene termonomer and the thermoplastic polymer is comprised of polypropylene. The rubbery polymer may be cross-linked EPDM having a clear surface, ethylene-propylene rubber and polypropylene, ethylene octene and the like. The thermoplastic polymer is comprised of uncrosslinked polyolefins that are thermoplastic. In a preferred embodiment, the thermoplastic polyolefin is a polymer of ethylene, propylene and diene monomers.
In one embodiment, the sheets are positioned adjacent one another such that a side edge of each sheet is contiguous and the fold strip overlaps the contiguous side edges. In another embodiment, the fold strip is positioned between the sheets and bonded to a side edge of the sheets to form a large width single-ply heat-weldable roof membrane.
It will be appreciated that the fold strip facilitates folding of the large width membrane along the fold strip without creating a permanent crease within the membrane.